Engine starter



Oct. 21, 1947. J. E. BUXTON ENGINE STARTER Filed June 23, 1944 1 N VENTOR.

Patented Oct. 21, 1947 ENGINE STARTER James E. Buxton, Elmira,

dix Aviation Corporation, corporation of Delaware N. Y., assignor toBen- South B end, Ind., a

Application June 23, 1944, Serial No. 541,702 6 Claims. (Cl. 29(l'38)The present invention relates to an engine starter, and moreparticularly to a starting system incorporating gearing of the type inwhich energization of the starting motor automatically effectsengagement of the gearing and such engagement is maintained until theengine is reliably self operative, whereupon the acceleration of theengine gear is permitted to disengage the gearing.

In starter gearing of the above indicated type, it is usual to providean overrunning connection to the starting pinion in order to prevent theengine from driving the armature of the motor which might cause it torotate at a dangerously high speed. The use of such clutches, however,has been found in some instances to make the demeshing of the pinionsomewhat sluggish and consequently noisy. Moreover, the types ofoverrunning clutch heretofore used have sometimes been undesirably noisyin operation.

It is an object of the present invention to provide a novel enginestarter of the type which maintains its engagement with the engine untilcontinuous self operation of the engine is secured,

incorporating means to insure prompt disengagement of the drive oncompletion of the starting operation.

It is another object to provide such a device in which engagement of thedrive is effected by acceleration of the starting motor, and promptdisengagement is insured by quick deceleration of the starting motor.

It is a further object to provide such a device in which the drive isheld in engagement by a latch which is automatically tripped at theconculsion of the starting operation.

It is another object to provide such a device in which the tripping ofthe 1atch is simultaneous with the deceleration of the starting motor.

It is another object to provide such a device incorporating anoverrunning clutch which forms a reliable and positive drivingconnection, and overruns freely and quietly.

Further objects and advantages will be ap parentfrom the followingdescription taken in connection with the accompanying drawing, in

which:

Fig. l is a side elevation partly in section of a preferred embodimentofthe invention; the electrical circuits involved being showndiagrammatically;

Fig. 4 is a section taken substantially on the line 2-2 of Fig. 1; and

Fig. 3 is a detail in perspective of the latch pin and its actuatingmember.

In the drawing there is illustrated a starting system including abattery I grounded at 2 and connected by a lead 3 to a starting switch 4conveniently located for control by the operator of the engine to bestarted. Switch 4 is connected by a lead 5' to the field windings 6 andI of a starting motor 8. At their other ends the fields 6 and l areconnected to the brushes 9 and II respectively, which conduct currentthrough the armature 12 to the brushes l3 and [4 which are grounded tocomplete the starting circuit.

Means are provided for connecting the starting motor 8 to rotate amember such as a flywheel gear of the engine to be started. For thispurpose, the starting motor is provided with an armature shaft l5 havinga smooth reduced extension 16, the reduction in diameter being definedby a thrust shoulder ll against which one or more thrust washers H arepreferably seated. On the outer end of the extension Hi there is rigidlymounted a driving head l8 as by means of a cross pin l9 retained by alock ring 26. The driving head l8 has a smooth cylindrical extension 2l, and a'screw shaft 22 is slidably journalled thereon and yieldablyconnected for rotation therewith by means of a torsion spring 23anchored at its ends to thedrivin'g head and screw shaft by means ofanchor plates 24 and 25. The anchor plates are non-rotatably mounted onthe driving head and screw shaft and have slots adapted to receive theout-turned ends 26 and 21 of the spring, respectively.

A pinion 28 is slidably journalled on the extension N5 of the armatureshaft for longitudinal movement into and out of engagement with a membersuch as a gear 290i the engine to be started. Means for traversing thepinion into and out of operative position and for rotating the pinion isprovided comprising a nut 36 threaded on the screw shaft 22 and rigidlyconnected at one end to a barrel member 3|. The opposite end of'thebarrel is connected to the pinion by means 'of an overrunning clutchcomprising a driving plate 32 anchored as indicated at 33 in the barreland having clutch teeth 34 on its face. A driven clutch member 35 isfixed as indicated at'36 on'the' pinion and has teeth 31 adapted toengage with the teeth 34 of the driving clutch member. Means areprovided for limiting the separation'of the driving and driven clutchmembers and for transmitting alight frictional drag from the pinion tothe barrel member, in the form of a thimble 38 anchored to the end ofthe barrel 3| as indicated at 33 and having a swivel connection 40 withthe pinion. A spring 4| located between the clutch members is arrangedto hold said members normally out of engagement.

According to the present invention means are provided for maintainingthe pinion 28 in engagement with the engine gear 29 until a successfulstart of the engine has been secured. As here shown this means comprisesa latch pin 42 slidably mounted in the control nut 30, and an actuatingmember therefor in the form of a ring 43 slidably but non-rotatablymounted on the control nut. Pin 42 is provided with a notch 44 adaptedto receive a reduced section 45 of ring 43 so as to couple the pin tothe ring for sliding movement in unison. The ring is retained on thebarrel by suitable means such as a lock ring 46.

The inner end of the pin 42 is preferably flattened as indicated at 41,and bears on the periphery of the screw shaft 22. Means for pressing thepin against the screw haft is provided in the form of a plunger 48slidably mounted in a recess 49 in the nut 3|] opposite the pin 42, anda compression sprin here shown as a rubber block 50 which presses theplunger 48 against the ring member 43. Screw shaft 22 is provided with anotch in position to receive the end of latch pin 42 when the barrelassembly has moved the pinion 28 into mesh with engine gear 29.Engagement of the latch pin in notch 5| thus holds the pinion in mesh.When the pin 42 bears on the periphery of the screw shaft, the outersurface of ring 43 is substantially concentric with the axis of thedrive. Entry of the pin into the notch 5|, however, allows the springpressed plunger 49 to slide the ring into a slightly eccentric position.

Means under the control of the operator are provided for tripping thelatch and at the same time causing rapid deceleration of the startingmotor in order to insure that demeshing of the pinion takes placepromptly and without interference between the teeth of the pinion andthe flywheel gear as the pinion moves out of mesh. In order toaccomplish this result, recourse is had to the electrical braking devicedisclosed in the patent to Janes, Number 2,353,900, issued July 18,1944, and assigned to the assignee of the present application.

For this purpose thejunctions of field coils 6 and 1 of the startingmotor with brushes 9 and I respectively, are connected by leads 52, 53and 54 to an electromagnet 55 which is arranged when actuated to close aswitch 56. Switch 56 controls a circuit which is in shunt with thestarting switch 4 and comprises a lead 51 connected to the battery lead3, a resister 58, a lead 59 and a lead 63 connected to the startingmotor lead 5.

The braking effect of the motor is secured as described in saidapplication by grounding the lead 54 which shortcircuits the armature |2of the starting motor while maintaining the energization of the fieldcoils 6 and 1. To this end a switch 6| is connected to the motor lead 54and by a lead 62 to the ground at 63.

According to the present invention the flow of current through thegrounding circuit 52, 53, 54, 6|, 62, 63 is used to Withdraw the latch42 from the notch 5|. For this purpose, a solenoid in the form of asingle turn coil 64 is inserted in the ground lead 62 which solenoid isarranged when actuated to project a finger 65 into the path of rotationof the ring 43. Engagement of the finger with the ring as it rotates,moves the ring into concentric relation with the axis of the drive,thereby raising the latch out of the notch 5| and freeing the barrel andpinion assembly for demeshing movement. The finger 65 is normally heldout of engagement with the ring 53 by suitable means such as a spring66.

Means are provided for closing the grounding switch BI andsimultaneously energizing the trip solenoid 64 immediately upon openingthe starting switch 4. As shown, this means comprises an electromagnet67 which is connected by leads 58 and 69 to the opposite ends of theresister 58 so that when a voltage drop occurs through the resister thatvoltage is impressed on the electromagnet to close said switch.

In operation, closure of the starting switch 4 by the operator causesenergization of the starting motor 8 in the usual manner wherebyrotation of the armature shaft I5 is transmitted through the spring 23to the screw shaft 22, and the nut 36 is traversed along the screw shaftuntil the pinion 28 engages the thrust washer l0. Since the longitudinalmovement of the pinion is thus arrested, it is compelled to rotate withthe armature shaft and thereby rotates the engine gear 29 with which itis in mesh. At this time, the latch 42 has entered the notch 5| of thescrew shaft under the pressure of the spring 50 so that backwardmovement of the barrel is limited by engagement of the latch in saidnotch. When the meshing movement of the pinion is arrested, furthermovement of the barrel compresses the spring 4| and closes the clutch32, 35 whereby the pinion is rigidly connected for rotation with thebarrel.

During the cranking operation rotation of the armature 2 of the startingmotor causes the generation of a counter E. M. F. in said armature whichvoltage is expressed between the brushes 9 and H and the ground. Thisvoltage is impressed upon the electromagnet 55 causing closure of switch56. Since the starting switch 4 is closed, however, there is no voltagedrop across the resister 58, and consequently the grounding switch 6|remains open.

When the engine fires, the pinion 28 is accelerated, backing off thebarrel 3| sufficiently to ermit the spring 4| to disengage the clutchmembers 32, 35 after which the pinion is free to overrun while furtherbackward movement of the barrel is prevented by the latch pin 42. If theengine does not continue self operative, it slows down until thestarting motor catches up with it and cranking 1's resumed, promptclosure of the clutch being assured by the light frictional connectionbetween the pinion and barrel provided by the swivel connection 49.

When the engine has become reliably self operative, the operator opensthe starting switch 4 whereupon the current through the starting motoris compelled to traverse the shunt circuit including the resister 58 andswitch 5'5. The consequent voltage drop across the resister 58 energizesthe electromagnet 61 to close the grounding switch 6! whichshortcircuits the armature 2 causing a powerful braking effect to beapplied to the starting motor. At the same time the coil 64 is energizedto bring the finger 35 into the path of the latch ring 43 thus trippingthe latch and permitting the nut 39 with its associated parts to betraversed back to idle position by the deceleration of the armatureshaft. As soon as the starting motor comes substantially to rest, thecounter E. M. F. of its armature dies out and the voltage across itsbrushes is reduced substantially to zero whereupon the electromagnet 55is deenergized, permitting switch 56 to reopen, thus breaking thestarting motor circuit and permitting the grounding switch 6| to openand the trip finger 65 to return to its idle position.

Although but one form of the invention has been shown and described indetail, it Will be understood that other embodiments are possible andthat various changes may be made in the design and arrangement of theparts without departing from the spirit of the invention as defined inthe claims appended hereto.

What is claimed is:

1. In an engine starting system a starting circuit including a startingmotor and a starting switch, means for rotating an engine from thestarting motor including a screw shaft, a nut threaded thereon, and apinion movable by the nut into and out of mesh with a gear of the engineto be started, a latch for holding the pinion in mesh with the enginegear, means responsive to opening the starting switch for retardingrotation of the starting motor and means responsive to actuation of theretarding means for tripping said latch.

2. An engine starting system as set forth in claim 1 including furtheran overrunning clutch connection between the nut and pinion.

3. In an engine starting system a starting circuit including a startingswitch and a startin motor controlled thereby having a field andarmature, means for connecting the starting motor to rotate an engineincluding a screw shaft, a nut threaded thereon and a pinion connectedto the nut for movement thereby into and out of mesh with a gear of theengine to be started, a latch for holding the pinion in mesh with theengine gear, a magnetic trip for the latch, means for shortcircuitingthe armature of the motor to arrest its rotation, said motor arrestingmeans including means for actuating the magnetic trip.

4. An engine starting system as set forth in claim 3 in which said motorarresting means is arranged to open the motor circuit and release themagnetic trip when the starting motor comes substantially to rest.

5. In an engine starting system, a starting circuit including a motorand a starting switch, means for driving an engine from the motorincluding a pinion movable into and out of engagement with an enginegear, means responsive to acceleration of the motor for moving thepinion into mesh with the engine gear, and operative on deceleration ofthe motor to return the pinion to idle position, means for holding thepinion in mesh with the engine gear, means actuated by the opening ofthe starting switch for applying a braking force to decelerate themotor, and means energized by said decelerating means to release saidholding means.

6. An engine starting system as set forth in claim 5 including further,an overrunning clutch connection between said moving means and thepinion.

JAMES E. BUXTON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,909,415 Maurer May 16, 19332,218,972 Kearney Oct. 22, 1944 2,339,486 Kearney Jan. 18, 19442,342,632 Hood Feb. 29, 1944 2,353,900 Janes July 18, 1944

